This application is based on and claims priority under 35 U.S.C. xc2xa7 119 with respect to Japanese Application No. 11(1999)-215564 filed on Jul. 29, 1999 and Japanese Application No. 11(1999)-276669 filed on Sep. 29, 1999, the entire content of both of which is incorporated herein by reference.
This invention generally relates to a head rest. More particularly, the present invention pertains to a head rest device for a vehicle seat for resting the head portion of a seated occupant.
To enlarge the vehicle interior space as much as possible, demands have been placed on vehicle manufacturers to reduce the thickness of the seat back. This is particularly so in the case of the front seat design to ensure that the occupants seated in the rear of the vehicle have a spacious area for their knees.
Vehicle seats are typically provided with a head rest and it is desirable that the position of the head rest be adjustable in the vertical direction to properly receive the head portion of the occupant of the seat. The position adjusting device for adjusting the vertical position of the head rest usually disposed in the seat back of the seat.
One known type of vehicle head rest device is disclosed in Japanese Utility Model Application Laid-Open No. H6(1994)-50547. This head rest device includes a guide member for a movable member of the head rest position adjusting device and a drive shaft for moving the head rest in the vertical direction. A portion of the panel of the device to which a motor is secured is used as the guide member for the head rest stay. The guide member and the drive shaft are disposed in the seat back of the vehicle seat assembly so as to be parallel to one another in the vehicle longitudinal direction.
However, because the guide and the drive shaft for adjustably moving the head rest in the vertical direction are disposed in line in the longitudinal direction of the vehicle, the position adjusting device mechanism occupies a thicker space in the longitudinal direction of the vehicle and thus does not leave sufficient space for the legs of the passengers seated in the rear seat.
Another known device is disclosed in Japanese Patent Application Laid-Open Publication No. H7(1995)-79837. This device includes a pair of bearings disposed in the seat back for slidably moving the head rest stay in the vertical direction. The bearings are positioned separately in vertical direction.
With this device, in order to have a more close contact of the passenger head portion with the head rest, the headrest is moved forwardly during upward adjustment of the head rest with respect to the vertical track. In this case, the vertical track actuating mechanism for the position adjusting device is adapted to minimize the seat back thickness.
However, this particular construction suffers from the drawback that the upward or downward movement of the head rest is performed with a fulcrum at the upper bearing where most of the load is concentrated on its small bearing surface. Thus the bearing itself has to have sufficient strength to endure such concentrated load at its pivotal points.
In light of the foregoing, a need exists for an improved vehicle seat head rest which is not susceptible to the same disadvantages and drawbacks as those mentioned above.
According to the present invention, a head rest device for a vehicle seat includes a stay member supporting a head rest and attached to the upper portion of a seat back of the vehicle seat. The stay member includes a pair of stay shafts extending downwardly from the head rest. A position adjusting device adjusts the head rest position relative to the seat back, with the position adjusting device being disposed in the seat back and including a drive motor, a drive shaft operatively connected to the drive motor and extending from the drive motor, a nut member in engagement with the drive shaft and vertically movable, a movable member secured to the nut member and vertically movable with the nut member, a guide member for guiding the vertical movement of the movable member, and a stopper member connecting the movable member with the lower end of each stay shaft of the stay member for restricting the vertical position of each stay shaft with respect to the movable member. The drive shaft and the guide member are disposed in the seat back in parallel with each other and extending downwardly. The drive shaft and the guide member are separately arranged in the lateral direction of the seat back of the vehicle seat.
The head rest device of the present invention enables the thickness of the seat back in the vehicle longitudinal direction to be minimized so that vehicle interior space is enlarged. Particularly, when the present invention is applied to a front seat, it is possible to provide additional leg or knee space for passengers in the rear seats, thus improving their comfort.
The head rest stay shafts have a bending portion bent rearward and so the head of the occupant may be closely contacted by the head rest cushion when the head rest is in use. Additionally, the head rest stay shafts of the head rest device are slidably supported by a larger bearing surface for receiving a load due to the same curvature or inclination of the bending portion of the stay shafts and the guide member slidably receiving the stay shafts. Further, in spite of the curved or inclined up and down track of the head rest device, the head rest position adjusting device adopts a linear movement actuating mechanism to minimize the thickness of the seat back.
According to another aspect of the invention, a head rest device for a vehicle seat includes a stay member attached to an upper portion of a seat back of a vehicle seat and supporting a head rest, with the stay member including at least one stay shaft extending downwardly from the head rest. A position adjusting device is disposed in the seat back for adjusting the position of the head rest relative to the seat back. The position adjusting device includes a drive motor, a threaded drive shaft operatively connected to and extending from the drive motor, a nut member threadably engaging the drive shaft and vertically movable along the drive shaft, a movable member secured to the nut member and vertically movable with the nut member, and a guide member for guiding the vertical movement of the movable member. The drive shaft and the guide member are disposed substantially parallel to one another and are spaced apart from one another in a plane extending in a lateral direction of the seat back.